Edit: in case I've misunderstood, you are correct that Barkskin should *Not* force your AC to be 16, and thus lower it, if your existing AC would be higher - it should not make the second example character's AC BE 16 - that character's AC should remain 18, and Barkskin would have functionally no effect unless their AC would otherwise drop below 16 (such as if they took off their armour and shield). If the game is currently *reducing* your already-higher AC to 16, that is indeed a bug and should be reported.
You hadn’t misunderstood! Or at least Barkskin isn’t touching my druid’s 17 AC when she’s wearing her armour and shield. It’s also not mentioned on the tooltip for her dire raven form AC which is naturally 16, whereas it is for the wolf with natural AC 14. This implies the game will only use Barkskin to calculate AC for a character whose AC is otherwise less than 16.
